Gas turbine



Feb. 26, 1963 Filed March 16. 1960 S. B. WILLIAMS ETAL GAS TURBINE 3 Sheets-Sheet 1 l l A f 2f ""J 1N V EN TORS'.

/M QQ@ Feb- 26, 1963 s. B. wlLLlAMs ETAL 3,079,068

GAS TURBINE Filed March 16.-- 19.60

3 Sheets-Sheet 2 EN ORS. /Zgdws .7277@5' if aF/v Feb. 26, 1963 s. B. WILLIAMS ETAL 3,079,068A

GAS TURBINE 3 Sheets-Sheet 3 Filed March 16, 1960 3,079,668 GAS TURBINE Sam E. Williams, Walled Lake, and John F. Innes, Berkley, Mich., assignors to Williams Research Corporation,

Walled Lahe, Mich., a corporation of Michigan Filed Mar. 16, 1960, Ser. No. 15,339 3 Claims. (Cl. 23d-127) This invention relates to gas turbines, and more particularly to diffusers for distributing air delivered from the centrifugal compressors of such turbines, or other centrifu'gal compressors.

The diuser associated with a centrifugal compressor 1n a gas turbine plays an extremely important role in determining over-al1 turbine efficiency, and it is an object of the present invention to provide an improved diffuser construction which is of high efficiency and at the same the possibility of interference between the diffuser vanes and the supersonic wake from the compressor vanes.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description, taken in conjunction with the accompanying drawings.

In the drawings:

FIGURE 1 is a side elevational view in cross-section of .a preferred embodiment of the improved diffuser, shown in conjunction with a radial compressor and adjacent por.- vtions of a gas turbine; I

FIGURE 2 is a front elevational View of the diffuser .taken in the direction of the arrow 2 of FIGURE l;

FIGURE 3 is an end elevational view of the diffuser vtaken in the direction of the arrow 3 of FIGURE l,.show

ing the exits from the spiraling passages;

FIGURE 4 is a fragmentary plan view of the inner diffuser member, taken in the direction of the arrow 4 of FIGURE 2, showing the cross-sectional shapes of the vanes; and

FIGURE 5 is a schematic view showing a method of machining the vanes and vane passages.

In-general terms, the diffuser comprises inner and outer annular members adapted to fit together in stationary fashion adjacent the outlet of a radial gas turbine compresser. One side of the inner member has a radial wall which is in spaced parallel relation with an end member of the gas turbine housing, so that a vaneless annular radial passage is formed contiguous with the outer ends of the compressor vanes. The inner diffuser member is formed with a radius at its outer edge leading to an axially extending section spaced inwardly from the outer member which is in the form of a ring. A plurality of spirallyshaped passages are formed in said axially extending space. These passages, which are created by vanes formed on the outer surface of the inner diffuser member, are of gradually increasing*cross-sectional area even though their outer diameter is constant, and the exits from these passages lead to the heated air chamber adjacent the gas turbine combustion chamber.

Referring more particularly to the drawings, the gas turbine is generally indicated at 11 and comprises a housing generally indicated at 12, a radial or centrifugal compressor generally indicated at 13, and a diffuser generally indicated at 14. Housing 12 comprises an end member 15 which has an inner axially extending portion curving into a central radial portion, the outer end of member 15 having a ange 16 which interlits with the flange '17 of a diffuser housing ring 18. Ring 18 forms the outer member of diffuser 14, the inner member of this diffuser being designated at 19 and described later in detail. The opposite end of ring 1S has a ange 21 intertting with the flange 22 of a housing shell 23, which forms a pressurized heated air chamber 24 outwardly of an annular combustion chamber 25.

Radial compressor 13 comprises a shaft 26 connected to a first stage turbine (not shown) and which carries a plurality of compressor vanes 27. These vanes have axially facing entrance portions and are curved spirally outwardly to form exit portions adapted to deliver cornpressed air with a spirally outward centrifugal flow. As will be noticed in FIGURE l, vanes 27 are in close relation with the inner surface of housing member 15.

Diuser 14 comprises annular inner member 19 and outer housing member 13. Inner member 19 has an inner hub portion 28 adapted to carry a bearing assembly 29 for shaft 26. An oil drain line 3f) for bearing assembly 29 is accommodated by radially aligned apertures 31 and 32 provided in members 19 and 18 respectively.

An inclined web portion 33 of frusto-conical shape extends outwardly from hub portion 28 of member 19, and the outer portion of member 19 is formed with a plurality of spirally-shaped vanes 34 as best seen in FIGURE 4, these vanes being described in greater detail below. The

forward side of member 19 has a radially disposed wall 35, so that a dead air space 36 is located between portions 33 and 35 of member 19. The forward surface 37 of wall portion 35 is in spaced parallel relation with the radial portion of housing end member 15, so that a space 3S is formed by these two members, this space being continuous with the exits of compressor vanes27. v A shouldered portion 39 isy formed along the annular inner edge of wall portion 35this ange having a close fit with the outer edge of compressor 13.

Theouter portion of wall 35 has a radius 41vwhich is continuous with wall surface 37 so that the surface curves into an axial orientation. End member 15 of the housing has a curved portion '42 approximately concentric with radius 41 so that annular passage 38 leads in a continuous manner to an axial disposition.

kVaries 34 have tapered leading edges '43 which start immediately past radius 41, as seen in FIGURE 4. The vanes are of suchangular disposition as to receive swirling air as it passes around radius 41 with a minimum of turbulence. Vanes 34 form passages 44 between them, the

inner surfaces 45 of these passages being formed on the body of member 19. Passages 44 are of continuously increasing cross-sectional area toward their exit ends, this being accomplished by a progressive reduction in the radial ydistance of surface 45 from the turbine axis, as is best seen in FIGURE 2.

A plurality of bosses yi6 are formed at the exit ends of vanes 34 as best seen in FIGURE 4, these bosses being contiguous with wall 33 of member 19 as will be observed in FIGURE l. Bosses 46 are provided for purposes of rigidity, and have apertures 47 for the reception of fasteners (not shown) which also pass through aligned apertures 48 in member 18.

Diffuser 14 is so constructed and shaped as to be capable of manufacture by relatively inexpensive methods, such as casting. In order to facilitate assembly of the two diffuser members, the inner surface 119 of member 18 has a slight outward taper in the direction of the main gas turbine area. Likewise, the outer surfaces 51 of vanes 34 are of slightly increasing diameter so that member 19 will fit snugly within member 18, as seen in FIGURE l.

In operation, air will be compressed by compressor 13 and will flow outwardly in a swirling manner into radially extending passage 38. As it reaches the outer portion 3 of this passage it will be guided into an axial direction by the space between radius 41 and curved portion 42 of housing member 15. The air lwill then enter passages 44 between vanes 34 and its kinetic energy will be converted to pressure by the increasing cross-sectional areas of these passages. The air will then exit into chamber 24 from where it may enter the combustion chamber.

It will be observed that the axial disposition of vanes 34 and passages 44 will greatly increase the compactness of the diffuser assembly by reducing the necessary total outside diameter, while still retaining the diffuser eiciency in terms of air travel and energy conversion. Passage 38 of the diffuser will also, of course, permit an increase in air volume because of its radial disposition. The increases in cross-section-which occur in passages 38 and 44 are accomplished without requiring excessive alterations in the air flow path and While maintaining a short total flow path. The fact that the first portion of the diffuser air passage is vaneless will reduce the possibility of interference with supersonic wake from compressor vanes 27. Preferably, the size of radius 41 is so chosen as to prevent turbulence of the air as it alters flow which might destroy or detract from the effect of the vaned diffuser portion. It should be kept in mind in this regard that the air will how in a semi-tangential manner around radius 41 because of its-swirling movement, the size of radius 41 being suilicient to prevent the creation of dead air spaces at the inner portions of passages 44.

FIGURE illustrates one step in a method of machining the vanes and vane passages of the diffuser. According to this method, inner diffuser member 19, indicated schematically by a rectangle in FIGURE 5, is supported for rotation on an axis S2., and a milling cutter 53 rotatable on an arbor 54 perpendicular to axis 52 is used to machine surfaces 45 as well ,as the llanks of vanes 34. For this purpose, tool 53 has cutting edges on its cylindrical surface as well as its lower end.

If it is desired that the inner portions of passages 44 (at the top of FIGURE 4) be on a cylindrical surface, -support axis 52 of member 19 will tirst be placed in a h orizontal position and arbor 54V on a vertical axis. The inner portion of each passage 44 and its adjacent vane 34 may then be machined by simultaneously rotating member 19 on its horizontal axis and advancing it in the direction of this axis. Support axis 52 and arbor :54 may then 'be inclined as shown in FIGURE 5, and machining of the main portion of each passage 44 continued by rotating member 19 on inclined axis 52 and simultaneously advancing member v19 in a horizontal directionas indicated by arrow 5S in FIGURE 5. The result of this combined motion will be the machining' of the vane flanks as helicoids and machining spirals of decreasing diameter for surfaces 45. The novel configuration of the diffuser thus greatly facilitates machining.

While it will be apparent that the preferred embodiment of the invention disclosed is well lcalculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

l. ln a diffuser for use in conjunction with a centrifugal compressor, .a first diffuser section comprising a vaneless annular passage having radially disposed walls and leading outwardly a substantial distance from the compressor outlet, a curved annular vaneless passage leading from the outer portion of said first section into an axial direction, a'secon'cl diffuser section having Van axially extending 'annular passage leading from said curvedpassage, and a plurality of vanes disposed within said axial passage, said vanes having leading edges disposed at the axial exit of the said annular vaneless passage, the total length of said radial and curved vaneless passages being suicient to prevent interference by said leading vane edges with supersonic flow from said compressor.

2. In a diluser for use in conjunction with a centrifugal compressor, an outer diffuser member comprising a ringlike housing element extending substantially axially, an inner diffuser member comprising an annular body having a radial wall portion the Vinner edge of which is adapted to be disposed adjacent the outlet of a centrifugal compressor, a curved outer annular edge on said radial wall portion leading to a plurality of spiral axially extending vaned passages of slightly increasing outside .diameter and progressively increasing cross-sectional area formed in the body of said inner diluser member, a web portion on said inner diffuser member leading inwardly from the exit ends of said passages, a bearing supporting portion formed at the inner edge of said web portion, said inner diffuser member being adapted to fit within the outer diffuser member with the outer edges of said vanes engaging the inner surface of the outer diffuser member to form said passages, and a housing member connected to one edge `of said outer diluser member and being in spaced parallel relation with said radial wall portion and curved edge of the inner diffuser member, whereby a radially extending annular vaneless passage will be formed leading outwardly from said compressor, and curved annular vaneless transitional passage will be formed leading from said radially extending passage to said axially extending passages, the leading edges of the vanes forming said axially extending passages being disposed at the axially extending exit of .said transitional passage, the total length of said radial and curved vaneless passages being sufficient to prevent interference by said leading vane edges with supersonic' how from .said compressor.

3. In a dithiser for use in conjunction with a centrifugal compressor, a rst diluser section having a radially .disposed annular vaneless passage with radially disposed "walls and leadingv outwardly a substantial distance from the outlet of said compressor, a second diffuser section extending axially from the outer portion of said -rst section, a plurality of vane-separated spirally extending -passages of progressively increasing cross-.sectional area disposed within said second diluser section, the outer portions of said spiraling passages being a slight but progres- .sivelyv increasing .distance and the inner portions being a progressively Shorter distance from the compressor axis .throughout their extent, and a curved annular vaneless transitional passage connecting the outer portion of said 'first passage with the entrances of said second passages, the 'leading edges of the Avanes in said second .diffuser section being disposed at the axially extending exit of said vaneless 'transitional passage, the total length of ,said radial and curved vaneless passages being sufficient to pre vent :interference by said leading vane edges with supersonic flow from said compressor.

References Cited in the tile of this patent UNITED STATES vPATENTS 2,405,048 Nickerson July 30, 1946 2,622,789 Lundquist z Dec. 23, i952 FOREIGN PATENTS 604,121 Great Britain June 29, 1948 661079 France g Feb. 26, 192-9 669,357 Great Britain c Apr. 2, 1952 

3. IN A DIFFUSER FOR USE IN CONJUNCTION WITH A CENTRIFUGAL COMPRESSOR, A FIRST DIFFUSER SECTION HAVING A RADIALLY DISPOSED ANNULAR VANELESS PASSAGE WITH RADIALLY DISPOSED WALLS AND LEADING OUTWARDLY A SUBSTANTIAL DISTANCE FROM THE OUTLET OF SAID COMPRESSOR, A SECOND DIFFUSER SECTION EXTENDING AXIALLY FROM THE OUTER PORTION OF SAID FIRST SECTION, A PLURALITY OF VANE-SEPARATED SPIRALLY EXTENDING PASSAGES OF PROGRESSIVELY INCREASING CROSS-SECTIONAL AREA DISPOSED WITHIN SAID SECOND DIFFUSER SECTION, THE OUTER PORTIONS OF SAID SPIRALING PASSAGES BEING A SLIGHT BUT PROGRESSIVELY INCREASING DISTANCE AND THE INNER PORTIONS BEING A PROGRESSIVELY SHORTER DISTANCE FROM THE COMPRESSOR AXIS THROUGHOUT THEIR EXTENT, AND A CURVED ANNULAR VANELESS TRANSITIONAL PASSAGE CONNECTING THE OUTER PORTION OF SAID FIRST PASSAGE WITH THE ENTRANCES OF SAID SECOND PASSAGES, THE LEADING EDGES OF THE VANES IN SAID SECOND DIFFUSER SECTION BEING DISPOSED AT THE AXIALLY EXTENDING EXIT OF SAID VANELESS TRANSITIONAL PASSAGE, THE TOTAL LENGTH OF SAID RADIAL AND CURVED VANELESS PASSAGES BEING SUFFICIENT TO PREVENT INTERFERENCE BY SAID LEADING VANE EDGES WITH SUPERSONIC FLOW FROM SAID COMPRESSOR. 